These studies are primarily aimed at transplantation of catecholamine-containing tissues, including adrenal medulla, tumor cells, and embryonic brain tissue into the brain. The purpose of these experiments is to elucidate the properties of these tissues after transplantation and the response of the host brain to the transplanted tissues. Specifically, these experiments employ non-primate animal models to (1) develop the techniques of brain tissue transplantation for clinical use in Parkinson's disease; (2) develop brain tissue transplantation techniques so that they eventually may be applicable to other disorders, such as schizophrenia or Alzheimer's disease if and when these disorders become well enough understood to permit such applications; and (3) elucidate factors that control the development of the brain and responses of the brain to injury or impairment, with particular emphasis on the nigrostriatal dopamine system. During the past reporting year, significant progress has been made in these areas.